Speechless, I sure don't know why the tech didn't explain anything. I know that the abdominal musculature responds differently if you are upright or supine and they want you prone to get accurate readings.
What are they testing you for?
Call a few radiology offices and find out if there is a way to accomodate you. With maybe a gap-table that would avoid pressure on the surgically sensitized area.
Try Florida Medical Clinic. Ask to speak with an EMG tech. They usually like to talk. You must have gotten a grouch.